Cartridge or plug-in pumps often are employed in those environments where the pump is housed within the confines of a tank or receptacle containing fluid to be delivered under pressure remote from the tank or receptacle. These cartridge or plug-in pumps, as they are frequently called, are so designed as to permit their ready removal from the tank or receptacle for replacement or repair. The pumps may be primary sources of fluid under pressure, or they may function as boost pumps to deliver the fluid from the tank or receptacle to another pump for final delivery to a system and use.
For example, in an aircraft environment, pumps of the character described typically are located on the bottom surface or the side wall of the fuel tanks to allow external access to the pump cartridge.
The fuel tanks may be at varying levels of fullness and the removal of the pump must be effected without the requirement of draining the fuel tank. Therefore, many such systems have valve constructions which are somehow operatively associated with the pump cartridge whereby removal of the pump cartridge automatically closes the valve to seal off the fuel tank from the pump housing and allow pump removal without massive fuel leakage. An example of such a system is shown in copending application Ser. No. 198,744, filed May 25, 1988, which is assigned to the assignee of this invention.
Still, with the above-described precautionary measures, a problem exists in verifying that the automatic shut-off valve actually has sealed the fuel tank before removing the pump cartridge. In other words, should the valve malfunction for some reason, removal of the pump cartridge would allow massive leakage from the fuel tank.
In U.S. Pat. No. 4,318,667 to Miller, dated Mar. 9, 1982 and assigned to the assignee of this invention, a pump inlet closure valve/actuating mechanism assures that the valve is closed prior to pump removal. It also effectively blocks removal of a drain plug prior to inlet closure valve actuation. However, the mechanism of Miller does not require that the drain plug be removed before the pump cartridge can be removed. Thus, there is no effective verification of inlet closure valve sealing prior to pump withdrawal.
This invention is directed to an improved system which employs a simple mechanism to allow valve closure, but prevents pump removal or withdrawal unless a drain plug on the pump cartridge has been removed, thus verifying an effective inlet closure valve seal. In essence, the invention uses a drain means on the pump cartridge to prevent removal of the cartridge from the pump housing unless the drain means is removed from the pump cartridge itself. In this manner, absolute verification of inlet closure is effected before the pump cartridge can be withdrawn.